In a previous blog post, I discussed cats and hyperthyroid disease. At that 
time you may have been wondering just why I didn’t mention dogs getting hyperthyroidism. The answer is that dogs do not tend to get hyperthyroid disease as cats do. Dogs tend to get the opposite disease which is hypothyroid disease.
Now, this isn’t to say that dogs never get hyperthyroidism, but it tends to be much rarer in our canine companions. Today, I will discuss hypothyroidism. I will remind you what the thyroid is and does, I’ll explain the signs and symptoms of this disease, and I’ll tell you ways to determine if your dog has it. In addition, I will describe the treatment options for canine hypothyroidism.
What is the thyroid?
The thyroid is a gland that is located about halfway down your pet’s neck. This gland sits near your pet’s trachea (sometimes referred to as a windpipe). This gland is controlled by a part of the brain called the pituitary gland. The thyroid gland’s job is to help regulate metabolism, or how the body changes food into energy.
What does HYPOthyroidism mean?
Hypothyroidism means that the thyroid gland is under-acting. This causes the body’s metabolism to slow down, so it is not burning calories into energy
as quickly or efficiently as it should. Just like in people, dogs with a slower metabolism tend to gain weight much quicker.
What causes hypothyroid disease in dogs?
The most common cause of hypothyroidism in dogs is idiopathic thyroid gland atrophy. I realize this sounds super doctor speak, so let’s break this down. “Idiopathic” means that we don’t necessarily know the reason why it is happening, and “thyroid gland atrophy” means that the gland shrinks up.
There are some theories that the dog’s own body sees the thyroid gland tissue as foreign and attacks it, turning it into fat instead. There are also some thoughts that this may be a heritable disease, meaning that it may be passed on from mom and dad dog to their pups. Another potential cause for this disease is thyroid cancer, which tends to be a much rarer cause.
What are the symptoms that my dog may show of this disease?
The most common signs and symptoms that you may see in your dog include:
- weight gain despite the amount of exercise or diet
- dull fur coat, fur thinning – typically on lower back and sides
- increased recurrence of skin or ear infections
- increased darkening of skin pigmentation
What can my vet do to determine if my dog has hypothyroid disease?
If your veterinarian thinks that your dog may have a thyroid disorder, she will most likely recommend some bloodwork. Your vet will want to run a thyroid blood panel that looks at the total thyroid level (T4) as well as the
thyroid-stimulating hormone (TSH) to help to diagnose if your dog has hypothyroidism. She may also order some other bloodwork to look at your pet’s overall health and organ function to make sure that there are not any other underlying health problems.
Are there ways to fix or treat this disease?
There is no “fix” of hypothyroidism per se, but there is treatment available for your dog. Treatment involves daily medication to help replace your pet’s thyroid hormone. This medication will be needed life-long.
Your veterinarian will want to do bloodwork approximately one month after your dog has been on the medication to check to make sure that your dog is at the correct dosage of the medication. Your vet may need to adjust thyroid medication dosing or she may find that the current dose is effective. The doctor will then help you to set up a plan for monitoring bloodwork and managing the disease moving forward.
Hypothyroid disease is a fairly common disease in dogs. If you are concerned that your dog is showing signs of hypothyroidism, please contact your vet to set up an appointment for an exam. Remember that with medications and careful monitoring, thyroid disease in dogs is a manageable problem.
Dr. Heintz is a small and exotic animal veterinarian at 
